There are many situations in which units of inventory and other items are labeled to assist in the identification and/or tracking of the items. The use of bar code labels on items for consumer purchase has become virtually universal. Bar code labels are also commonly used by shipping companies to identify packages being shipped. Another technique for identifying items is to apply radio frequency (RF) tags to the items. The tags may be active, i.e. transmit identifying signals without being queried by an outside source, or passive, i.e. provide an identifying signal only when activated by an inquiry signal. In the latter case, the inquiry signal is sufficient to energize the tag to enable the sending of the identifying signal. An advantage of RF tags, as opposed to bar codes, is that the orientation of the tag and the inquiring apparatus with respect to each other is noncritical in the case of the RF tags. An example of a type of RF tag is the tag sold by Texas Instruments under the trademark TIRIS. As used herein, the term "RF tag" is used broadly to include any type of magneto resonant tag.
The inventors perceived that it would be advantageous to embed RF tags into thermal or thermal transfer bar code labels or bar code labels produced by other printing processes. One approach would be to embed the tags at media conversion plants where the label media is prepared from large rolls of material by cutting the rolls into desired widths and, as appropriate, die cutting the reduced width sections of the rolls to produce the desired lengths of the labels. This approach has a number of serious drawbacks that make it impractical. First, several hundred different lengths and widths of die-cut labels are in common use. Label media and the material used to produce it typically include label stock, made from paper or plastic, having a front face for printing and an opposite back face with adhesive thereon, and a liner adjacent to the adhesive to prevent the adhesive from sticking to adjacent coils of label stock or other items prior to application of a label. The machinery required to apply RF tags between the labels and liner and then die cut the labels for all possible label sizes would be prohibitively expensive and complicated.
Another serious problem is that, once tags are applied to the labels, their additional and uneven thickness would cause serious problems in rewinding the converted stock into rolls. This drawback is present equally whether the conventional label stock/liner material is used or a type of linerless media is used. Because of considerations of waste and environmental protection, interest in use of linerless media has been increasing. The converted stock, with or without a liner, when wound into rolls, would have an uneven thickness that could cause the rolls to telescope. The increased thickness would also the reduce the number of labels which can be wound on a standard diameter roll to one-third the normal number. Another problem is that, in the current state of the technology, not every tag in a roll of tags is functional because of low production yields. If the tags are applied at the media conversion plant, each bad tag would result in the loss of a label.
Perhaps the most significant problem is the problem of printing over the tag area on a label that has a pre-applied RF tag. Even small RF tags occupy two square inches of area. Within this area, the overall media thickness increases from a nominal 0.007 inch (for label, liner and adhesive) to 0.011 inch. The portion of the tag on which the silicon chip is located is even thicker, with a nominal thickness of 0.022 inch. This last thickness would ordinarily require that no printing be allowed within a certain distance of the chip location. On small labels, this requirement could prevent any printing at all. The best situation that could be hoped for is that the labels would have to be reformatted to accommodate the "no-print zone". Such reformatting would cause additional time and expense and would be unacceptable to at least most customers of suppliers of printers and label media.
The present invention seeks to provide labels having electronic, e.g. RF, tags while avoiding the problems discussed above in relation to embedding the tags at the media conversion plant where the label media is prepared for sale and shipment to customers.